Study On Mechanical Effects Of Adjacent Construction On Existing Tunnel And Optimization Of Control Parameters

Currently, with the increase in construction of metros, there is many successful cases of adjacent constructions, but there few research in the field of multi-way cross, close-space, multi-construction method and multi-structure form. In the future more and more problems will appear in the large number of urban underground constructions. In the field, it will become a focus problem that how to ensure the safety of building and exsiting tunnels in progress of constructions and operations. This thesis takes the the engineering practice of Shenzhen Metro Line No.2,3tunnel down-traversing the existing Shenzhen Metro Line No.1,4of as study subjects and researched the adjacent construction to provide reference for the similar projects.Firstly, a lot of research and case analysis have been done on adjacent construction at home and abroad. The mechanism of impact on the adjacent construction and measures are analyzed theoretically.Secondly, based on the engineering practice of the Shenzhen Metro Line No.2,3tunnel down-traversing the existing Shenzhen Metro Line No.1,4, numerical simulation method is used to establish the corresponding three-dimensional finite element model.In different construction conditions, the mechanical behavior of the main structure features and deformation of existing tunnel are analyzed after the building tunnel transfixion and during excavation in order to determine mechanical laws and the safety impact of the existing tunnel.Based on these analyses, reasonable reinforcement measures are made to provide a reliable basis in the construction of the new-tunnel.Finally, blasting construction of mined tunnel (the building-tunnel) is simulated based on calculations theory of LS-DYNA. Additional stress, displacement and velocity of the existing tunnel are analysed during the construction to determine force, displacement and vibration regulation of the structure of the existing tunnel. Combined with operational safety standards of the existing tunnel, reasonable controlling parameters are proposed to ensure the safe operation of existing tunnel.